Genetics Answers

Male cats are either black (B) or orange (O). Females are black, orange, or calico, which has patches of black and orange. Calico is formed from the codominance between the two alleles in the heterozygote, so a calico cat is (X^B X^O).  Give the genotype and phenotype ratio of a cross between an orange male cat and a calico cat.

The trait that is masked by the dominant trait is the _____ trait.

recessive

cross

purebred

hybrid

which color is dominant in a bird, gray or black? How do you know?

1. Each mutant shown below was derived from the wild type:

Wild type 5' GAA CTC GAG CTT AAT 3'

Mutant 1 5' GAA CTC GAG CTT AAT 3'

Mutant 2 5' GAA CTC AAG CTT AAT 3'

Mutant 3 5' GAA CTC GAG CTT AAT 3'

Classify the mutation at both the DNA and protein levels.

23. What is a carrier? If a carrier mates with a homozygous dominant individual, what 

are the chances one of their kids will get a disease?

24. If a heterozygous parent has a disease caused by a dominant allele and mates with 

a homozygous recessive individual, what are the chances that their child will get the 

disease?

19. A child has type O blood, and her mother has type A blood. What is the mother's 

genotype? What are the possible genotypes for the father?

20. What is the difference between pleiotropy and polygenic inheritance? Give an 

example of a trait that exhibits each.

21. What makes a good study organism for genetic research? Give an example of a 

bad study organism and a good one.

22. Be able to interpret a pedigree chart and say what possible genotypes the children 

of two known parents can produce.

14. What does Mendel's law of segregation say? When in meiosis does this 

segregation occur?

15. How can two organisms have the same genotype but different phenotypes? For 

instance, why aren't identical twins (who have the same DNA) exactly the same in 

every way?

16. What does the law of independent assortment say? When in meiosis does 

independent assortment occur? In what cases does this law not hold true?

17. Can you draw Punnett Squares for crosses of up to 2 genes at once? If I tell you 

that alleles are completely dominant, incompletely dominant, epistatic, or 

codominant, can you tell me which genotype codes for which traits? Can you draw 

Punnett squares for sex-linked traits?

18. Be familiar with how the ABO blood types work. What kind of dominance do the 

alleles for blood types show?

10. When Mendel crossed a purple-flowered pea with a white-flowered pea in the P 

generation, all the offspring were purple, but the white flower trait reappeared in the 

F2 generation. How can a trait disappear in one generation and reappear in the 

next?

11. If you see a 3:1 ratio in the offspring from a genetic cross, what does this tell you 

about the genotypes of the parents?

12. If tall height (T) is dominant to short height (t) and purple flowers (P) are dominant 

to white flowers (p), what fraction of the offspring from the cross TtPp x ttPP will be 

short and purple?

 13. Let's you crossed a true breeding plant that produces lethal poison with a true 

breeding plant that produces no poison for the P generation. All of the F1 

generation produce mild poison. 1/4 of the F2 generation produce lethal poison, 1/4 

produce no poison, and 1/2 produce mild poison. What kind of dominance is this an 

example of?

6. In what kind of situation would you want to perform a test cross? How would you do 

it?

7. Suppose that a certain breed of dogs has either floppy or pointy ears, and this trait 

is controlled by one gene with two alleles. Pointy ears are dominant over floppy 

ears. You have a pointy-eared dog and want to know whether it is homozygous or 

heterozygous. What would you do?

8. If you cross a true-breeding homozygous dominant individual with a true-breeding 

homozygous recessive individual, what will be the genotypes and phenotypes of the 

F1 generation? If you cross the F1 generation with each other, what will be the 

genotypes and phenotypes of the F2 generation?

9. In humans, having free earlobes (F) is completely dominant over having attached 

earlobes (f). If a man with free earlobes marries a woman with attached earlobes, 

and all of their kids have free earlobes, what is most likely the genotype of the 

father? Can you be completely sure of the father's genotype? Why or why not?

1. What type of dominance(complete, incomplete, or codominance) best fits the 

Blending hypothesis? What type fits the particulate hypothesis?

2. What is a character (a gene)? What is a trait (an allele)? If I say that information at 

one locus on a chromosome codes for either blue or orange flowers, can you tell 

me what is the gene and what is the allele?

3. What is a genotype? What is a phenotype? If I ask you to write the genotype and 

phenotype for a heterozygous flower from one of Mendel's pea plants, can you do 

it?

4. What do we mean by P, F1, and F2 generations?

5. What do we mean by "true-breeding" or "pure?" What do we mean by "hybrid?" 

What is a monohybrid cross? What is a dihybrid cross?